CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2009

  • question_answer
    If the lines\[\frac{1-x}{3}=\frac{y-2}{2\alpha }=\frac{z-3}{2}\]and\[\frac{x-1}{3\alpha }\]\[=y-1=\frac{6-z}{5}\]are perpendicular, then the value of\[\alpha \]is

    A)  \[\frac{-10}{7}\]                              

    B)  \[\frac{10}{7}\]

    C)  \[\frac{-10}{11}\]           

    D)         \[\frac{10}{11}\]

    E)  \[\frac{10}{9}\]

    Correct Answer: A

    Solution :

    Given lines can be rewritten as \[\frac{x-1}{-3}=\frac{y-2}{2\alpha }=\frac{z-3}{2}\] and        \[\frac{x-1}{3\alpha }=\frac{y-1}{1}=\frac{z-6}{-5}\] Since, lines are perpendicular. \[\therefore \]  \[{{a}_{1}}{{a}_{2}}+b{{ & }_{1}}{{b}_{2}}+{{c}_{1}}{{c}_{2}}=0\] \[\Rightarrow \]               \[(-3)(3\alpha )+2\alpha (1)+(2)-5=0\] \[\Rightarrow \]               \[-9\alpha +2\alpha -10=0\] \[\Rightarrow \]               \[\alpha =-\frac{10}{7}\]


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